Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$125.70	12.654%	$141.6061	$141.61	$141.60	$141.60
Purchase #2	$95.93	3.490%	$99.278	$99.28	$99.30	$99.30
Purchase #3	$22.47	5.575%	$23.7227	$23.72	$23.70	$23.70
Purchase #4	$134.98	11.407%	$150.3772	$150.38	$150.40	$150.40
Purchase #5	$56.98	13.175%	$64.4871	$64.49	$64.50	$64.50
Purchase #6	$200.79	6.209%	$213.2571	$213.26	$213.25	$213.30
Purchase #7	$120.69	5.705%	$127.5754	$127.58	$127.60	$127.60
7 purchase totals =	$757.54		$820.3036	$820.32	$820.35	$820.40